The present invention describes a method and apparatus for mixing ceramic powder and binder for injection molding. More particularly, the present invention discloses a method of mixing ceramic powder and binder in which metallic contamination from the mixer is eliminated.
The mixing of ceramic powder and binder for ceramic injection molding represents a critical step in the fabrication process for injection molded parts. The mixing equipment used for this process is, however, almost exclusively metallic. This combined with the long duration of batch compounding cycles (typically 1 to 4 hours) leads to significant metallic contamination of the ceramic mix. Study of fractured ceramic components often identifies such particulate contamination i.e. high density inclusions (HDIs) as the source of failure.
An additional drawback of batch type compounding is the need to largely fill the mixing cavity for best mixer performance. There is therefore no way to produce a high quality mix using only very small batches of ceramic powder (for QC or experimental purposes).
The present invention avoids these constraints while eliminating contamination from metallic parts.